Stratified-charge, compression ignited diesel engines can provide considerably higher thermal efficiency than spark-plug ignited homogenous-charge combustion engines but require fuels with high cetane rating to provide ignition by air that has been sufficiently preheated by rapid compression. Combustion chamber compression ratios of 16:1 to 22:1 are typically required for compression ignition systems of engines designed to use diesel fuel with an appropriate cetane rating. There is great interest in using alternative and/or renewable fuels interchangeably with diesel fuel in existing engines to reduce fuel costs and reduce exhaust emissions compared to diesel fuel.
However, long standing problems have defeated numerous attempts to use spark ignition in high compression engines. Such problems include: failure of narrow spark gaps to reliably ignite fuel-air mixtures at high compression pressures; failure of inductive coil voltage boosting ignition systems due to inadequate containment and delivery of the voltage required for spark production in highly compressed air; and failure of capacitance discharge systems due to failure to contain the voltage required for spark production in highly compressed air.
In many cases, these failures are the result of voltage containment failures of materials such as engineering polymers and spark plug porcelain that have provided satisfactory voltage containment for combustion chambers of relatively low compression engines. Other failures include capacitive dissipation, conduction and arc-propagation, along with cracking, spalling, and phase changes of conventional materials due to the high voltage magnitudes required in high-compression engines.
Accordingly, there are urgent needs for improved ignition and/or fuel system components that have the capability to provide an adequate spark discharge at electrode gaps of 1 mm (preferably greater) and for cylinder pressures of 700 PSIG and greater in order to facilitate applications of alternative and/or renewable fuels interchangeably with diesel fuel in existing engines.